The invention relates to driving circuits, and more particularly, to signal driving circuits with a precise output analog voltage level and high driving capability.
To reduce total module costs and time-to-market of display systems, “system-on-glass” technology of low temperature poly-Si (LTPS) TFTs offers a promising solution due to integration of driving circuit on glass. In conventional display systems, digital-to-analog conversion is the most important part of a signal driving circuit, such as a source/data driver. Typically, a digital-to-analog converter (DAC) requires a unit-gain analog buffer to improve driving capability thereof, as shown in FIG. 8A. However, because TFTs have poor performance, such as poor uniformity and high driving voltage, analog buffers composed of TFTs always have a large DC offset voltage, resulting in large difference between input and output analog voltage levels. If there is no analog buffer at the output of the DAC (as shown in FIG. 8B), either the driving capability of the DAC is insufficient or the power consumption of R-string voltage reference circuit is high when the DAC is a resistive DAC (R-DAC).